Detection, Understanding and Control of Soybean Mosaic Virus

Among 67 or so viruses that are able to infect soybean, 27 are considered a threat to the soybean industry (Tolin and Lacy, 2004; Saghai Maroof et al., 2008). Soybean mosaic virus (SMV) is the most prevalent virus and is recognized as the most serious, long-standing problem in many soybean producing areas in the world (Wang, 2009). SMV is a member of the genus Potyvirus in the family Potyviridae. The disease caused by SMV was first documented in the USA in 1915 by Clinton (1916) and SMV was named by Gardner and Kendrick (1921). Since then, the virus has been found in China, Japan, South Korea, Canada, Bazil, Australia and many other countries wherever soybean is grown. Infection by SMV usually results in severe yield losses and seed quality reduction. It has been reported that yield losses usually range from 8 to 50% under natural field conditions (Hill, 1999; Arif and Hassan, 2002) and reach up to 100% in severe outbreaks (Liao et al., 2002). Since SMV is a seed-borne viral pathogen and aphids can efficiently spread it from plant to plant while they feed, it is difficult to control the virus and produce SMV-free seeds. Furthermore, SMV often infects soybeans with other viruses such as Bean pod mottle virus (BPMV), Alfalfa mosaic virus (AMV) and Tobacco ringspot virus (TRSV) (Wang, 2009). Such synergistic infections with two or more viruses cause much more severe damages than infection by each virus alone (Hill et al., 2007; Wang, 2009). Utilization of soybean cultivars resistant to SMV is considered the most effective way of controlling the diseases. Extensive screening for soybean gemplasm resistant to SMV has resulted in the identification of three independent resistant genes, i.e., Rsv1, Rsv3, and Rsv4 (Hayes et al., 2000; Gunduz et al., 2002; Liao et al., 2002; Zheng et al., 2005; Li et al., 2010a). Interestingly, several naturally occurring resistance-breaking SMV isolates have also been reported that can break all three or two soybean resistance loci (Choi et al., 2005; Gagarinova et al., 2008a). The development of durable genetic resistance to SMV becomes a research priority for soybean breeders and soybean pathologists. This may depend on advances in the understanding of the SMV life cycle and molecular SMV-soybean interactions.